5V and 12V seem to be within acceptable ranges (even though 5V seems a bit high), and to be honest I wouldn't worry too much about the low -12V rail, my LC PSU has a very low -5V rail as well but works fine otherwise.

I'd just try starting it up once you get the ROM's sorted out

I suppose you could always try the PSU in your SE (if you're signature is still up to date ).